This invention relates to sizing paper and paper products including paperboard.
For some time now alkenyl succinic anhydrides ("ASA's") have been used in sizing for paper products, to improve characteristics such as water and ink holdout and chemical resistance. Wurzburg et al., U.S. Pat. No. 3,102,064, Wurzburg U.S. Pat. No. 3,821,069, and Wurzburg 3,968,005 disclose the use of various ASA's for this purpose.
ASA's tend to be hydrophobic, and they generally must be used in aqueous paper manufacturing systems. Considerable effort is required to achieve a uniform, stable ASA emulsion suitable for paper manufacture
In particular, Warzburg '069 discloses the use of cationic agents (e g., various starch derivatives), together with other emulsifiers. Specifically, at 6:34-49, a corn starch ether dispersion is prepared in boiling water, and then ASA is slowly added with high-speed dispersion. The resulting stock emulsion is diluted and added to aqueous pulp slurries.
Mazzarella Re 29,960 (U.S. Pat. No. 4,040,900) discloses adding a liquid ASA sizing mixture directly to an aqueous paper stock system with low shear forces, using certain polyoxyalkylene aryl or polyoxyakylene alkyl-aryl ethers as emulsifiers
Rende U.S. Pat. No 4,657,946 discloses the use of cationic water-soluble vinyl addition polymers and condensation polymers to emulsify ASA's. This procedure includes dispersing ASA in aqueous solutions of the vinyl additives polymers using a high speed or high-shear disperser and then diluting the resulting emulsion (8:23-28).
Shepard U.S. Pat. No. 4,207,142 and Hiskens et al. 4,222,820 disclose specific classes of ASA sizing agents which are emulsified to form sizing compositions.
Novak U.S. Pat. No. 4,606,773 discloses emulsifying ASA paper sizing agents using a cationically modified water-soluble polymer in conjunction with water-soluble cationic starch.